Kill Step Validation Model for Bakery Applications

Brian Strouts AIB International

Outline:

q  Introduction

q  Kill-Step Validation Gen-1: •  Foundational research project: Hamburger bun kill-step

validation research •  Baking Process Kill-Step Calculator

q  Kill-Step Validation Gen-2:

q  Expected outcomes

q Approximately 2,800 commercial bakeries and 6,000 retail bakeries operate in the U.S., with a market value of nearly $30 billion/ year (Hussain 2014).

q  The U.S. baking industry comparatively has a very safe record for

the production of shelf stable processed foods q Microbiological spoilage is often the major factor limiting the shelf

life of bakery products leading to huge economic losses (Smith et al. 2010)

q Although not directly linked to production practices, there were 4,200 illnesses associated with bakery products reported in the U.S. between 1998 and 2011 (CSPI 2009)

Introduction Introduction

q  The presence of Salmonella spp. in bakery ingredients and products could create a public health risk if the product is improperly baked

q  Research findings revealed that Salmonella can survive in adverse conditions (e.g., low moisture foods) for a long time (Gruzdev et al. 2011 and Eglezos 2010)

q  Pathogens such as Salmonella spp. can be introduced into bakery products through a wide range of ingredients such as egg (Board 1969; FSIS 1998), milk products (El-Gazzar et al. 1992; Ahmad et al. 2000), flour (Richter et al. 1993; Dack 1961), milk chocolate (D’Aoust 1977), coconut (Goepfert 1980), peanut butter (Scheil et al. 1998), fruit (Golden et al. 1993), spices (Hara-Kudo et al. 2000) and yeast flavorings (Joseph et al. 1991)

Bakery Products: Food Safety Challenges? Bakery Products: Food Safety Challenges

q  Although most bakery products undergo a putative kill step at the point of production, such as baking or cooking, there lacks published scientific proof or validation research q  FDA-FSMA regulatory requirement requires validation and verification of kill-step

q A preemptive scientific evaluation providing documentary evidence that a particular process is capable of consistently delivering a product, meeting its pre-determined specifications

q A collection of scientific evidence

Validation

The need… The Need….

q  What would constitute validation? (§117.160(b)(2)): The proposed rule would require that the validation of preventive controls include collecting and evaluating scientific and technical information or, when such information is not available or is insufficient, conducting studies to determine whether the preventive controls, when properly implemented, will effectively control the hazards that are reasonably likely to occur

q  Must be performed (or overseen) by a preventive controls qualified individual; or q  Within 90 calendar days after production of the applicable food first begins; or q  Whenever a change to a control measure occurs; or q  Whenever a reanalysis of the food safety plan reveals the need to do so;

Key FSMA Validation Requirement Key FSMA Validation Requirement

q We used hamburger bun manufacturing as the model to develop a scientific validation protocol, as it is one of the most popular bakery products consumed in the U.S. and in Canada.

q  This is the first study of its kind involving validating a bakery product with baking as a kill step for Salmonella spp., E. faecium and Saccharomyces cerevisiae

Hamburger Bun Kill-Step Validation Research Hamburger Bun Validation Research

Research Collaborators Research Collaborators

To validate a simulated commercial baking process for hamburger buns to destroy Salmonella spp., and to determine

the appropriateness of using non-pathogenic surrogates (Enterococcus faecium ATCC 8459 or Saccharomyces

cerevisiae) for in-plant process validation studies

Goal Goal

1.  Validate the baking process as a kill step in reducing Salmonella spp. during the manufacture of hamburger buns

2.  Validate the baking step’s effectiveness in reducing S. cerevisiae and E. faecium to determine appropriateness of utilizing non-pathogenic surrogate for industry validation and process verification purposes, and

3.  Determine the heat resistance viz, D-value, and z-value of Salmonella spp., S. cerevisiae and E. faecium in hamburger bun dough

Research Objectives Research Objectives

q  Salmonella serovars: §  Salmonella enterica serovar Typhimurium (ATCC 14028) §  Salmonella enterica serovar Newport (ATCC 6962) §  Salmonella enterica serovar Senftenberg (ATCC 43845)

q  Enterococcus: §  Enterococcus faecium (ATCC 8459)

q  Yeast: §  Saccharomyces cerevisiae (Compressed Yeast)

Microorganisms Used in this Research Microorganisms Used

q  Two trays (35.6 cm x 21.6 cm x 14 cm) of flour containing 400 g each were mist inoculated with 4 mL of the target culture to achieve 6-7 log10 CFU/g q  This inoculation procedure was conducted within a Class II Type A2 biosafety cabinet q  After 5 min, trays of inoculated flour were placed into a 37ºC incubator until they returned to pre-inoculation dry weight q  Inoculated flour was stored at ambient temperature for 36-48 h prior to use q  Final target bacterial concentrations of the flour were determined immediately prior to initiation of mixing the dough

Flour Inoculation Flour Inoculation

Salmonella spp. Enterococcus spp.

1 43

6

2

5 7 8

Hamburger bun kill-step validation research Overview

Figure 1. Survival population of Salmonella serovars, Enterococcus faecium and Saccharomyces cerevisiae, in hamburger buns during baking at 218°C (using selective media)

DL

Results Results

DL

and Saccharomyces cerevisiae, in hamburger buns during baking at 218°C (using injury recover media) Survival population of Salmonella serovars, Enterococcus faecium and

Saccharomyces cerevisiae, in hamburger buns during baking at 218°C

Microbial kinetics study Table 1. D-values (min) and z-values (°C) of a 3-strain Salmonella spp. cocktail, and Enterococcus faecium ATCC 8459 in hamburger bun dough

Salmonella spp. E. faecium

BHI/XLDa XLDb BHI/mEAc mEAd

Temperature (°C)

55 28.64 ± 5.19 21.30 ± 2.61 133.33 ± 0 87.21 ± 4.74

58 7.61 ± 0.61 7.53 ± 0.61 55.67 ± 9.0 45.33 ± 6.79

61 3.14 ± 0.32 2.29 ± 0.21 14.72 ± 4.11 6.14 ± 0.47

z-value 6.68 ± 0.94 6.22 ± 0.32 6.25 ± 0.80 5.20 ± 0.05

a Injury-recovery media, Brain Heart Infusion (BHI) agar with Xylose Lysine Desoxycholate (XLD) agar overlay; b Selective medium, XLD agar; c Injury-recovery media, BHI agar with m-Enterococcus (mE) agar overlay; d Selective medium, mE agar. Salmonella cocktail: S. enterica serovar Typhimurium (ATCC 14028); S. enterica serovar Newport (ATCC 6962); S. enterica serovar Senftenberg (ATCC 43845)

Microbial Kinetics Study

Temperature Bun dough

52 18.73 ± 0.72

55 5.67 ± 1.51

58 1.03 ± 0.21

z-value 4.74 ± 0.34

Table 2. D-values (min) and z-value (°C) of Saccharomyces cerevisiae in hamburger bun dough  

D-values

Figure 3. Mean internal temperature profile of hamburger buns during baking at 218°C oven temperature for 13 min followed by 30 min of cooling

Internal Temperature Data

q  No viable Salmonella serovar cells were enumerated by direct plating on selective or injury-recovery medium (detection limit of 0.22 log CFU/g), or after selective enrichment after the minimum 9 min of baking q  E. faecium on both selective and injury-recovery media were observed up to 11 min of baking q  No viable yeast cells were detected after the 9 min baking point q  It is likely that the yeast were actually inactivated to undetectable levels at shorter baking times.

Results Results

q  The crumb temperatures increased to ~100°C during the first 8 minutes of baking, and remained at this temperature for the next 6 min q  The greater D- and Z-values of Salmonella spp. and E. faecium as determined on the injury-recovery media confirms that a sub- population of injured bacterial cells is able to survive heating in dough at the three temperatures studied q  D and Z values of S. cerevisiae were much lower compared to those of Salmonella spp. and E. faecium

Results (cont'd) Results (cont)

q  The data clearly demonstrates that the typical hamburger bun baking process utilizing oven temperatures ≥ 218.3°C (425°F) is extremely efficient in reducing very high levels of Salmonella spp. (>6 log CFU/g) for all baking times q  For the first time there is a scientific proof that a normal baking process can reduce Salmonella population by > 6 log cfu/g. q  E. faecium demonstrated greater thermal resistance compared to Salmonella spp. and S. cerevisiae q  Considering the internal temperature vs. time recorded in this study, it is clear that all the Salmonella cells were destroyed within 9 min, prior to the optimum bake time (as determined and utilized in these studies).

Conclusions Conclusions

q  The low thermal tolerance of S. cerevisiae relative to Salmonella limits its usefulness as a potential surrogate for process validations q  Greater survival of E. faecium during bun baking and higher D- values of E. faecium compared to that of Salmonella spp. suggest that E. faecium can be used as a surrogate for Salmonella spp. for baking studies in processing facilities, if needed q  Thermal resistance ranking:

E. faecium > Salmonella serovars > S. cerevisiae

q  It is necessary and valuable to conduct additional research involving multiple baked goods categories to demonstrate similar effects reported in this study

Conclusions (cont'd) Conclusions (cont)

Manuscript submitted to the “Journal of Food Protection” Manuscript Publication

Highlights from July 20th, 2015 FDA Meeting: Venue: FDA headquarters, Washington D.C., USA.

q  A first study presented to the FDA that indicated a proactive, industry approach to comply FSMA - The preventive controls for human foods (PCHF) rule

q  FDA had positive comments on AIB’s intent to design kill-step validation protocol for bakery products and provide on-site support, and training for US baking industries

q  Overall, the FDA liked the kill-step validation research done so far, and thought the bakery products selected for the next phase were appropriate, and

q  Interaction with the FDA will continue as we design and carry out next generation bakery product validation studies

Baking Process Kill-Step Calculator (BPKC)

•  Objective: •  The BPKC is designed to assist bakers in evaluating the

lethality of their process for destruction of Salmonella spp. in a variety of bakery products

BPLC: How it Works?

q  A microbial kinetics based interactive spreadsheet/calculator q  Based on internal temperature and time parameters

BPLC: How it Works?

Simple Procedure q  Download the BPKC to your computer from AIB's website q  Download the temperature profile (time-temperature data) from a data

logger to an Excel sheet q  Format the temperature profile (time-temperature data), such that the

time is in intervals of one minute and the temperature is in °F q  Enter at least 20 time-temperature data points to BPKC to accurately

calculate the lethality of the process

q  NOTE: Format the time such that you include at least the temperature data from 120°F during heating to the same temperature while cooling the product. It is acceptable to change the time intervals to larger values (such as ≥2 min) in case the process is longer and the product is at temperature 120°F for longer periods of time

Microbial Kinetics: Terminologies

•  D-Value: This indicates time in minutes at a constant temperature, that is necessary to destroy 90% or 1 log of the organism present at a given reference temperature.

•  z-Value: This is the temperature increase required to reduce the thermal death time by a factor of 10.

•  The z-value is constant for a given microorganism strain in a given product.

•  F-Value: This is the process lethality or the time in minutes, at a specific temperature required to destroy a certain number of viable cells.

BPKC: How it Works?

D value, Z value and

T-ref

Time x Temp data obtained from the

MOLE® data logger

Process lethality in terms of log

reductions

D, Z and T-ref are obtained

from AIB’s KSV study

BPKC: Output q  Determines F - value and cumulative F - value q  Automatically determines the total process lethality (e.g., 5 log) for Salmonella q Generates three graphs: Product internal temperature, F value/min and cumulative log reductions

Benefits of BPKC:

•  If the desired log reduction is achieved for the baking process and pathogen of concern, the process lethality report generated can be used as guidance and as a supporting documentation for

•  FSMA validation and verification process

Additional Research is Important Because …

q  There are more than 2,000 bakery products in the market. q  Bacteria respond/behaves differently at varying moisture levels,

pH, fat content etc. e.g., Salmonella has shown the highest resistance in low water activity and high fat foods.

q  Hence, it is necessary and valuable to conduct additional research involving multiple baked goods categories with varied moisture contents, pH, water activities (aw) etc.

q  Also, it is important to publish the next generation baking validation research findings, thus providing documentary evidence for the benefit of bakery industry’s food safety needs.

Major Bakery Products Category

Pan Bread

White, wheat

Whole wheat multigrain

Sweet Breads

Large pan Formats

Hearth/Artisan

Dinner Rolls

Par Baked

Dense Breads

Bagels

Chemical leaven products

Muffins

Cookies

Crackers

Snack cakes

Laminated dough products

Croissants, puff pastries

Filled products

Cinnamon rolls

Biscuits

Complex multicomponent

products

Prebaked pies

“Fruit cake" style products

KSV Gen- 2 Validation Research:

Baking Validation Next Generation Research: Criteria and Justification W

hole

gra

in w

heat

br

ead

•  Size (1lb loaf)

•  High moisture •  High water

activity (aw) M

uffin

s •  Chemically leavened

•  High sugar •  High moisture •  High fat

Coo

kies

•  Chemically leavened

•  Multi-component

•  Low moisture •  Low water

activity (aw)

KSV Gen 2: Research Objectives

•  Validate the baking process as a kill step in reducing Salmonella cocktail (S. Typhimurium, S. Newport, and S. Senftenberg), and

•  Determine the heat resistance pattern viz, D-value, and Z-value of Salmonella spp. during the baking process

Figure 3. Mean internal temperature profile of hamburger buns during baking at 218°C oven temperature for 13 min followed by 30 min of cooling

0

1

2

3

4

5

6

7

8

9

Flour Batter 13 min 15 min 17 min 19 min 21 min B+C

log

CFU

/g

Detection limit (0.2 log CFU/g)

BHI XLD

≥5Log CFU/g reduction

Salmonella spp. (3-strain cocktail) counts of muffins during 21 min of baking at 375°F (190.6°C) and 30 min of ambient air cooling (B+C).    

Figure 3. Mean internal temperature profile of hamburger buns during baking at 218°C oven temperature for 13 min followed by 30 min of cooling

0

1

2

3

4

5

6

7

8

9

Log

CFU

/g

Salmonella Population in Bread during Baking

BHI XLD

Detection limit (0.07 Log CFU/g)

≥5 log CFU/g redution

Salmonella spp. counts (7-strain cocktail) in bread during 35 min of baking at 375°F (190.6°C) and 60 min of ambient air cooling (B+C).

Short and long term benefits of this research to the baking industry

q  Pathogen free bakery products, assuring greater safety possible

q  Protects consumers, builds confidence q  Helps in determining an effective treatment option q  Demonstrates compliance to the FDA-FSMA act. q  Can help bakery industries avoid repetition and

duplication use of resources for kill-step validation research, and

q  Offers a pathogen inoculation option for companies with limited resources and capabilities.

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References

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